Temperature and electric field patterns at the end of microwave processing.

In this study, COMSOL®4.2a is used to model a microwave heating process in a TE10 rectangular waveguide. The sample consists of a small cylindrical Ca-alginate gel (D = 8 mm, H = 10 mm) inoculated with bacteria Escherichia Coli K12. The sample is placed along the microwave propagation direction into the waveguide. Maxwell’s equations and heat transfer are coupled to a microbial inactivation model under dynamic heating conditions. The microwave inactivation of bacteria is compared to a conventional inactivation by conduction with the same heating ramp during 4 min 30 s. The study clearly demonstrates that the microwave heating of small cylindrical sample is not homogeneous under dynamic heating conditions resulting in lower bacteria inactivation comparing to conventional heating.